1. Field of the Invention
The present invention relates to an image processing apparatus and image processing method, which corrects a blur of image capturing data that occurs due to vibration.
2. Description of the Related Art
A digital image easily allows an enlarged-scale displays to be displayed over 100% when using a personal computer. In an enlarged image, an image blur caused by even the slightest camera shake will stand out. For this reason, as image capturing devices for digital cameras gain higher resolutions, a process for correcting a camera shake that occurs at the time of imaging has received a lot of attention.
An image-stabilization method includes those implemented by hardware and software. In the hardware method, a gyro sensor is mounted on a camera, and the effects of a camera shake are eliminated by driving a lens and image capturing device to cancel vibrations of the camera during exposure based on an output signal from the gyro sensor. An image-stabilization method by means of a lens optical system is described in, for example, Japanese Patent Laid-Open No. 2002-214657.
The hardware image-stabilization method poses problems about an increase in number of components and that in manufacturing cost. When a similar function is to be implemented in an inexpensive digital camera, a software image-stabilization method is demanded.
In the software image-stabilization method, a method of synthesizing an image obtained by short exposure (to be referred to as a short exposure image hereinafter) and that obtained by long exposure (to be referred to as a long exposure image hereinafter) has been proposed (for example, Japanese Patent Laid-Open No. 2002-258351). Also, a method of acquiring a plurality of short exposure images, and synthesizing these images has been proposed (for example, Japanese Patent Laid-Open Nos. 2006-74693 and 2006-86762).
The method of Japanese Patent Laid-Open No. 2002-258351 corrects high-frequency components of the long exposure image using the short exposure image to recover an image blur. The method of Japanese Patent Laid-Open No. 2006-74693 aligns a plurality of short exposure images obtained by time-division exposure, so as to reduce their difference, and synthesizes these images, thereby recovering an image blur. Likewise, the method of Japanese Patent Laid-Open No. 2006-86762 synthesizes a plurality of images after blur correction while aligning their positions, thereby recovering an image blur.
However, the methods of Japanese Patent Laid-Open Nos. 2006-74693 and 2006-86762 suffer the following problems. In order to appropriately recover an image blur, a plurality of short exposure images are appropriately synthesized according to their displacement amounts. In other words, the appropriate image blur recovery process requires the accurate acquisition of displacement amounts. Therefore, a vibration amount between a given short exposure image and that captured immediately before or after that image has to be calculated. However, a process for accurately calculating a vibration amount and that for deforming and synthesizing images in correspondence with the vibration amount require very high calculation cost, resulting in a continuous shooting speed drop and a decrease in number of image capturing data that can be buffered.